Preliminary study of an angiographic and angio-tomographic technique based on K-edge filters

"Digital Subtraction Angiography is commonly affected by artifacts due to the patient movements. during the acquisition of the images without and with the contrast medium. This paper presents a. preliminary study on an angiographic and angio-tomographic technique based on the quasisimultaneous. acquisition of two images, obtained using two different filters at the exit of an X-ray. tube. One of the two filters (K-edge filter) contains the same chemical element used as a contrast. agent (gadolinium in this study). This filter absorbs more radiation with energy just above the so. called K-edge energy of gadolinium than the radiation with energy just below it. The other filter. (an aluminium filter in this study) is simply used to suppress the low-energy contribution to the. spectrum. Using proper calibration curves, the two images are combined to obtain an image of the. contrast agent distribution. In the angio-tomographic application of the proposed technique two. images, corresponding to the two filter types, are acquired for each viewing angle of the. tomographic scan. From the two tomographic reconstructions, it is possible to obtain a threedimensional. map of the contrast agent distribution. The technique was tested on a sample. consisting of a rat skull placed inside a container filled with water. Six small cylinders with 4.7mm. internal diameter containing the contrast medium at different concentrations were placed inside the. skull. In the plain angiographic application of the technique, five out of six cylinders were visible,. with gadolinium concentration down to 0.96%. In the angio-tomographic application, all six. cylinders were visible, with gadolinium concentration down to 0.49%. This preliminary study. shows that the proposed technique can provide images of the contrast medium at low concentration. without most of the artifacts that are present in images produced by conventional techniques. The. results encourage further investigation on the feasibility of a clinical implementation of the. technique."